Numerous tubular shaft instruments and thus also numerous tubular shafts are known from the related art. For example, European patent application EP 0577 423 A2 discloses a classic tubular shaft instrument in which a push and pull rod can be moved back and forth axially in its own shaft to allow the jaw part of the tubular shaft instrument to open and close. In this process, the back-and-forth movement of the push and pull rod is transmitted to the halves of the jaw part via a joint mechanism. The push and pull rod can be constructed as a rigid rod. This principle does not facilitate the production of bent tubular shafts.
Tubular shaft instruments with bent tubular shaft are also already known from the related art. For example, the German patent application DE 195 20 717 A1 discloses a tubular shaft instrument having a bent tubular shaft. This tubular shaft instrument employs a shaft having a straight proximal area and bent distal area. In the straight proximal area a rigid rod is used as push and pull rod, to the distal end of which a flexible push and pull rod is attached. The flexible push and pull rod is comprised of a rod in which a plurality of circumferential groves is incorporated, which reduces the cross-section of the rod such that the originally essentially rigid rod becomes flexible. Segments are left between the grooves where the push and pull rod retains its original diameter. These segments enable the push and pull rod to be correctly guided and supported in the bent section of the shaft. The push and pull rod tends in the bent shaft segment to assume not the intended shape of an arc, as it is prescribed by the bent area of the shaft, but rather the shape of a polygonal curve. In this context the number and spacing of support segments determines the shape of the polygonal curve. However, a tubular shaft constructed in this manner can be provided only with a single bend area.
If multiple bent areas are supposed to be provided on a tubular shaft instrument that are to be connected, for example, by straight sections, the entire push and pressure rod must be formed with grooves and support segments, because such type of tubular shaft cannot otherwise be assembled. The straight rigid sections then cannot be pushed through the bends in the shaft. However, if a push and pull rod that is equipped with grooves and support segments over the entire length is used, the inner friction of the tubular shaft is increased greatly. This is because a push rod soft enough to bend tends to deviate laterally and to press against the shaft from inside, which leads to additional friction. With a straight rigid rod, this virtually never happens. Additionally, with a push and pull rod that is flexible throughout its entire length, the play between the actuation unit on the proximal end of the tubular shaft and the functional unit on the distal end of the tubular shaft increases, which compromises the operation of the instrument.